1. Field of the Invention
This invention relates to release devices for releasing a chemical vapor into a space over an extended period of time.
2. State of the Art
Treatment of storage facilities with chemicals of various types has been practiced in various agricultural businesses. The treatment may be with chemical vapors, dusts, powders or the like, such as the treatment of potato storage facilities with sprout inhibiting chemicals.
Considerable study and innovation have been directed towards inhibition of potato sprouting during storage in large storage facilities. U.S. Patents to Hitchcock et al., U.S. Pat. No. 2,341,868; Luck, U.S. Pat. No. 4,078,480; Vaughn, et al., U.S. Pat. No. 5,129,951; Morgan, U.S. Pat. No. 4,887,525; and Plant, U.S. Pat. No. 3,128,170 describe various treatments to prevent sprouting in storage facilities.
Potatoes when being dug are frequently bruised, cut and/or abraded. These injuries to the potatoes oftentimes cause spoilage during shipment, storage and the like. A process known as suberization occurs naturally which tends to heal many of these injuries. However, whenever potatoes are stored, which occurs with a particularly large portion of potatoes harvested in any given year, if healing occurs slowly, a significant loss of potatoes can occur through spoilage. Early treatment with certain sprout inhibitors, such as CIPC, may retard the suberization process, thus contributing to the loss of potatoes through spoilage.
For example, it is relatively common in the potato storage industry to treat potatoes with Chloroisopropyl-N-carbamate (CFPC) to prevent or retard development of sprouts in the potatoes. Even though untreated potatoes are stored at a cool temperature, for example, generally between about 40xc2x0 and 45xc2x0 F., sprouting does begin to occur after a month or more of storage. Storage of upwards of six to eight months is typical for a stored potato harvest. Thus, without treatment of a chemical such as CIPC, the stored potatoes become entangled in sprouts and the whole stored lot of potatoes may become economically useless. Although early treatment with CIPC could be advantageous for sprout inhibition purposes, application of CIPC is typically delayed until after suberization has occurred inasmuch as CIPC tends to retard suberization, resulting in accelerated rot and spoilage.
Testing of isomers of dimethyl naphthalene (DMN) as a potential sprout inhibitor was conducted by placing alumina particles containing DMN in a box of potatoes stored at 10xc2x10.5xc2x0 C. in a ventilated cooler for a period of 12 weeks. The potatoes evidenced sprout inhibition in comparison with a control batch, i.e., in an untreated batch, and with a batch treated with Tecnazene, a commercial sprout inhibitor. Beveridge, et al., The Assessment of Some Volatile Organic Compounds as Sprout Suppressants for Ware and Seed Potatoes, Potato Res. 24 (1981) 61-76 and Beveridge, et al., Dimethyl Naphthalene as a Sprout Suppressant for Ware and Seed Potatoes, Potato Res., 24 (1981) 77-88.
The use of DMN treatment in a large storage facility has also been proposed. In PCT application PCT/GB92/01482 (Int""l. Pub. No. WO 93102563) of Everett-Todd, a system for monitoring the vapor pressure of alkyl naphthalenes is disclosed wherein alkyl naphthalenes are added to the facility when the monitored vapor pressure of alkyl naphthalenes falls below a certain value, e.g., 5 mg of alkyl naphthalene per cubic meter of storage free space.
While considerable effort has been devoted to sprout prevention of potatoes stored in larger facilities, little or no effort has been devoted to prevention of sprouting of potatoes during shipment. Freshly dug and stored potatoes are shipped to commercial markets, e.g., restaurants and the like, and to consumer markets, e.g., retail grocery stores, in refrigerated trailers and railroad cars. No other particular effort has been made to inhibit sprouting during the shipping and distribution process.
The instant invention relates to release devices which are structured to slowly release vapors of a sprout-inhibiting chemical into small packages of potatoes during shipment or storage. The device includes a quantity of porous media, i.e., a carrier, containing a significant amount of a potato sprout inhibitor, particularly a sprout inhibitor which is liquid at room temperature. The porous media is preferably a very fine particulate, inorganic material such as silica gel having a very high surface area per unit volume. The porous media is confined by containment means which is at least partially porous or permeable to vapors of the sprout inhibitor. Containment means may be made of any suitable material such as paper, cardboard, plastic, metal or fabric. It may be either rigid, semirigid or flexible. A suitable container may be in the form of a small canister or pouch or other convenient shape arid form for holding a significant quantity of the sprout-inhibitor-treated, porous media.
The release device may further be structured wherein a removable or breachable seal means encloses at least that part of the containment means which is porous or permeable. The seal means may be a plastic film or membrane which is substantially impermeable to the sprout inhibitor vapors. It could also be a metal tab that is sealed to a portion of the containment means so that removal of the tab exposes a porous region of the containment means.
The release device of the instant invention is intended particularly for packaged potatoes which are packaged in plastic bags, net bags, fabric bags, cardboard boxes or similar small containers. Potatoes generally having a weight of 5, 10, 25, 50 or 100 pounds or less are so packaged. While significant attention has been given to the treatment of potatoes in large storage facilities to prevent sprouting, little attention has been given generally to the problem of sprout inhibition of potatoes stored in small packages or shipped in small packages.
While very large volumes of freshly dug potatoes are sent to storage sheds for long-term storage, which is generally in excess of several months, a significant portion of a freshly dug crop of potatoes may be placed directly into boxes or packages for prompt shipment to market. These boxes or packages may be stored for short periods of time before being shipped and during the shipping process from the farm to consumer. For example, distribution centers may store potatoes for a period of days or weeks after receipt of the packaged potatoes from various producers. Also, potatoes which are removed from large storage facilities are packaged in smaller packages generally referred to as xe2x80x9cfresh packsxe2x80x9d for ultimate sale to consumers.
Even though potatoes at a storage facility may have been treated with sprout inhibitor, the sprout inhibitor application in such a storage facility is at a level to prevent sprouting at relatively low temperatures, that is, at preferred storage temperatures of about 40xc2x0 or 45xc2x0 F. or slightly elevated therefrom. Upon shipment of potatoes in small packages, temperature control may be irregular. For example, shipment of freshly dug potatoes in the early fall via truck, rail car and the like may result in the potatoes experiencing temperatures in excess of 80xc2x0 F. or more while being loaded, unloaded, etc., even when temperature control is a feature of each shipping vehicle. Since the potatoes are respiring and generating heat, the temperature within a confined railroad car or enclosed trailer may greatly exceed optimum storage temperatures. Thus, inhibition of sprouting during shipment is very desirable since sprouting is accelerated by temperatures above the optimum storage temperatures of 40xc2x0-45xc2x0 F.
The release devices of the instant invention are intended to be utilized with potatoes in ventilated packages. Potatoes packaged for shipment to consumers generally are placed in plastic bags with holes, in mesh bags or in boxes with ventilation holes. These holes are necessary to provide ventilation to prevent excess humidity buildup and to allow the potatoes to xe2x80x9cbreathe.xe2x80x9d As indicated, potatoes, even after long-term storage, respire and produce materials which preferably are allowed to escape, for example, carbon dioxide id moisture. Also, the ventilation is desirable to preclude excessive buildup of heat.
As indicated hereinabove, the sprout-inhibitor release device comprises a container for holding a porous media, especially a particulate media, substantially saturated with a liquid potato sprout inhibitor. The container may be either totally porous or permeable, wherein the pores are sufficiently small such that very fine inorganic, particulate media does not escape. The container porosity is such as to allow the vapors to escape at a rate sufficient to provide a significant vapor pressure of the sprout inhibitor in the package of potatoes. The release devices may be constructed in various sizes so that one size is appropriate for a five-pound package of potatoes and another size (twice as large) is appropriate for a ten-pound package of potatoes and so forth. Alternatively, the release device could be in one size, that is, a size suitable for a five-pound package of potatoes with multiple release devices placed in larger packages.
Generally, it is very desirable that the particulate media not be permitted to become loose in a package inasmuch as it could be lost through the ventilation holes during handling. Also, it could become stuck to potatoes and inadvertently ingested by a consumer. Thus, the containment means must have sufficient integrity and strength to endure the handling of packages going into storage, out of storage, into and out of transportation vehicles, into and out of warehouses, into retail stores and into the consumer""s home.
Generally, for the purposes of the instant invention, particulate media which is a silica material is preferred. Materials such as silica gel have a very high adsorption/absorption capacity for liquid sprout inhibitors. For example, significant quantities of an isomer of DMN may be readily absorbed upon silica gel. Also, the silica gel permits the release of vapors of DMN, for example, at a fairly predictable rate. Other inorganic materials such as diatomaceous earth, feldspar, zeolites and porous clays and other inert, porous materials may be suitable as an inorganic particulate media.
Preferred sprout inhibitors are isomers of dimethyl naphthalene with 1,4-dimethyl naphthalene being especially preferred. The 1,4-DMN isomer is a very effective sprout inhibitor and is readily absorbed by silica gel. The 1,4-isomer of DMN is also a volatile component of potatoes and is released by potatoes during storage. Provision of an increased vapor pressure of DMN in ventilated packages of potatoes during storage and shipment is desirable in precluding the sprouting of the potatoes. Also, 1,4-DMN isomer is generally not toxic to human beings and is not otherwise detrimental to the potatoes. This is an important factor inasmuch as the release devices of the instant invention are contemplated as being used with freshly dug potatoes. While some sprout inhibitors such as CIPC may retard the suberization or healing process of wounds, abrasions, etc. which potatoes experience during harvesting, 1,4-DMN appears to promote the suberization process.
The release devices of the invention may be provided with a sealing means although the release devices may be advantageously used without such sealing means. For example, release devices without sealing means may be placed in large numbers in a large can, which is then sealed and placed in a refrigerated area to reduce significantly the vapor pressure of the sprout inhibitor. Stored in this fashion, the release devices lose very little, if any, sprout inhibitor through vaporization. When the release devices are to be put into packages of potatoes, the large container may be removed from the refrigerated area and brought to a packaging process site, and the release devices immediately placed into packages of potatoes.
If the release devices are provided with seal means, then the release devices, after manufacture, would not need to be stored in any protective fashion which limits either vapor pressure or loss of vapors of the sprout inhibitor. Sealed devices could be stored at ambient conditions. Sealed release devices have the seal means removed or compromised when the release device is placed into a package of potatoes to permit vapors emanating from the porous media to escape into the package to initiate sprout inhibition.
Further understanding of the invention may be facilitated by reference to the attached drawings.